We are using signaling theory to explore how identity is presented and perceived in online environments. The fundamental idea is that many qualities we are interested in knowing about others are not directly observable. Instead, we rely on signals that are more or less reliably correlated with the quality. Sometimes signals are very reliable indicators of a particular quality, but sometimes they are not. The power of signaling theory is that it provides a means of evaluating the reliability of signals. We are using this approach to analyze social networking sites, reputation systems, graphical representations, and humanoid agents.